This invention relates to a vacuum breaker and backflow prevention device for a faucet.
Devices of this type are known in the art and are used to ensure that polluted or contaminated water is not able to flow backwards through the faucet to contaminate the water supply. Without such a device, a failure of the water supply could result in a loss of pressure and a vacuum condition which could suck water back into the supply pipes from a hose connected to a faucet and, for example, having an outlet end sitting in a pool of contaminated water.
U.S. Pat. No. 3,171,423 of Dillon issued Mar. 2, 1965 relates to a device of this type. The patent discloses an arrangement having a spring-biased valve member which can be forced open by normal water pressure. At the same time, a diaphragm covers vent holes in the device to prevent water flowing through them. In the event of a vacuum condition at the valve inlet, or back-pressure at the outlet, the valve member closes on a seat and at the same time lifts the diaphragm so that the outlet portion of the device is vented to atmosphere, thus preventing any water from being drawn or forced into the faucet and hence into the supply pipe.
A somewhat similar arrangement is disclosed in U.S. Pat. No. 3,459,443 of Butters et al issued Aug. 5, 1969, although that patent primarily relates to a tamper proof coupling so that that device cannot be easily removed from a faucet.
Canadian Patent No. 667,544 of Woodford issued July 30, 1963 also relates to a device of this type, but with a different type of means for preventing removal of the vacuum breaker from a faucet.
Canadian Patent No. 667,548 relates to a vacuum breaker device, similar to those of the above patents, but uses a slitted diaphragm which is biased upwardly by a spring pushing against a spider element.
A problem with prior art vacuum breakers is that water can be trapped by them which could freeze in the winter, causing damage to the vacuum breaker and outside piping. This problem is recognized in Canadian Patent No. 667,544 which provides a means for draining the upstream piping which involves unscrewing it sufficiently to open the drain openings 8 to atmosphere. It is also known to provide a vacuum breaker with a knob which can be pulled, after the hose is removed, to allow water within the vacuum breaker to drain out. Pulling on the knob opens the valve member.